It is estimated that at least 45% of all adults snore occasionally and 25% are habitual snorers. Snoring may decrease a person's ability to have a good night's sleep creating conditions for daytime sleepiness. Snoring is a sign of upper airway resistance and is one of the precursor indicators to obstructive sleep apnea (OSA). OSA is a condition that affects an estimated 14 million Americans. The condition is caused by relaxation of the soft tissue in the upper airway during sleep, resulting in obstruction of the upper airway. The obstruction can occur in nasal passages, in the upper pharyngeal or in the lower pharyngeal areas. OSA is characterized by a complete cessation of breathing during sleep for 10 or more seconds (apnea), or a reduction in breathing for 10 or more seconds causing a 4% decrease in blood oxygen level (hypoapnea). Individuals having 5 or more apneic or hypoapneic events per hour are diagnosed as suffering from OSA. The obvious side effects of sleep apnea are daytime sleepiness and chronic fatigue. However, OSA is known to be a contributing factor in hypertension, heart disease, as well as other serious health conditions.
Snoring is defined as the sound made by vibrations of tissue in the upper airway corresponding to vibrations of obstructions in the nasal passages 13, the soft palate, the genioglossal muscle or the epiglottis, as shown in FIG. 1. This region is known as the upper airway and is defined as that portion of the respiratory tract beginning at the mouth and nose and ending at the larynx (voice box). These vibrations are caused by turbulence inside the airway during inspiration or expiration. The turbulence is caused by a partial blockage that may be located anywhere from the tip of the nose 12 to the vocal chords. Snoring vibrations can originate from the oropharynx soft palette 14 and other associated objects such as the tonsils and adenoids or making contact with the upper region of the back of the throat 20 as shown in FIG. 2, the base of the tongue 10 vibrating against the mid-region of the back of the throat 30 as shown in FIG. 3, or from the epiglottis 18 vibrating against the lower region of the back of the throat 40 as shown in FIG. 4. The back of the throat is generally designated by reference numeral 16 in FIGS. 1-4. The specific points of contact causing snoring in a patient are designated by reference numerals 20, 30 and 40 as discussed above.
Current diagnostic practices test for the presence of snoring and may go so far as to quantitatively measure the snoring intensity or frequency distribution and power spectrum of the snoring sound. During a polysomnogram (diagnostic sleep test) one of three sensing devices are used. A microphone may be used to pick up the auditory snoring signal. This sensor suffers from artifacts, as it is able to pickup many other sounds other than snoring. A vibratory snoring sensor may be used to measure the vibration caused by snoring. This sensor is designed to pickup any vibration that occurs on the neck and as such will typically have movement and heart beat artifacts embedded within the signal. The third sensing device is a nasal pressure cannula. This device will measure the variations in the airflow signal that are assumed to be due to snoring. This sensor only functions if the pressure wave due to the vibration proceeds either out the nasal passage or oral passage and that the cannula captures enough of the pressure wave to register on the sensor element. Each one of these sensor devices is designed to output a signal based on whether there is snoring or not.